1. Field of the Invention
The present invention relates to a pulse synthesizing circuit.
2. Description of the Related Art
Conventionally, delta sigma modulation (ΔΣ modulation) is used in switching amplifiers or the like. A delta sigma modulator has an integrator, a quantizer, and a quantization error feedback circuit.
FIG. 9 illustrates a basic configuration of a delta sigma modulation circuit. A subtracter 16 calculates a difference between an input signal and a feedback signal, and an integrator 10 integrates the difference signal. An integral signal is quantized by a quantizer 14 and is output as, for example, one-bit (=binary) signal. The quantization error is fed back via a delay device 12.
JP 2007-312258 A discloses a delta sigma modulation circuit including an integrator group, an adder group, a quantizer, and a pulse width round-up circuit, and further discloses that a signal is converted into a one-bit signal synchronized with a sampling clock so as to be output. In addition, JP 2007-312258 A discloses that a D-type flip-flop is used as the quantizer. JP 2012-527187 W also discloses a delta sigma modulation circuit. Further, JP H10-233634 A discloses a configuration in which a quantized output signal that is obtained from an input analog signal and is output from a delta signal modulation unit is made to be a ternary signal, and positive voltage application, application off, and negative voltage application are set as switching control signals according to the ternary signal so that the switching control signals are output.
When pulse synthesis is performed in order to output the quantized output signal subjected to the delta signal modulation as a ternary signal, JP H10-233634 A is based on a premise that an output from the quantizer is a multi-valued (ternary or more) signal, and thus has a problem that versatility is lacking.